When it comes to blending in, the Atlantic longarm octopus
is a pro, expertly changing color to match the sea floor. But when invisibility
just won't do, this octopus has another trick up its eight sleeves: Make like a
flounder.

Researchers have captured photos and video of the Atlantic
longarm octopus mimicking the peacock flounder, a common flatfish that shares a
sandy habitat with the octopus in Caribbean waters. The Atlantic longarm
reverses the usual octopus arrangement, swimming forward instead of backward,
arms trailing behind like flounder fins. It swims along the contours of the sea
floor, even torquing its soft body so both eyes move to the left, just like a
flounder.

"The animals have good camouflage, but when they move,
motion gives away camouflage," Roger Hanlon, a senior scientist at the
Marine Biological Laboratory at Woods Hole, Massachusetts, and lead author of
the study, told LiveScience. "Instead of trying to be camouflaged while
they're moving, which is difficult if not impossible, they turn themselves into
flounder."

Clever creatures

Marine biologists have long known that octopuses are wily
creatures. They've been seen building
mobile homes out of coconut shells, and occasionally cause havoc in
aquariums by disassembling valves or short-circuiting lights. They're also
masters of camouflage, with color-changing skin and contortionist bodies that
can blend in with rocks and algae.

But few octopuses have been known mimics. In biology, mimicry
refers to an animal pretending to be another animal, like a moth playing
copycat to a spider to avoid being eaten. Two species of Indonesian octopus
have been seen mimicking flatfish, and the male of one species of cuttlefish
disguises itself as female to sneak by larger males and mate with real females.
Cuttlefish, octopuses and squid are members of a group of animals called
cephalopods. That makes the Atlantic longarm the fourth confirmed instance of
cephalopod mimicry and the first in the Atlantic Ocean.

"Most of the dramatic behavior we've seen from
cephalopods has all come from the Pacific," Jean Boal, a marine biologist
at Millersville University who wasn't involved in the study told LiveScience.
"So our plain little homegrown octopuses are doing some cool stuff."

In 2004, Hanlon and a group of volunteers were diving off
Saba Island in the Netherlands Antilles when one of them announced that he'd
seen an octopus mimicking a flounder. Hanlon didn't believe it at first, but
the man had snapped a picture. The next year, Hanlon and another volunteer
group went back and spent 51 hours diving before finally spotting another
flounder-mimicker. Gradually, the team acquired images and video footage from
other divers, eventually finding the behavior in octopuses in five locations
around the Caribbean.

The researchers aren't sure why the flounder inspires
mimicry. Octopus predators like eels and grouper often dart in to nip off a
soft, unprotected arm or two, Hanlon said, so impersonating a harder-bodied
flounder might make the longarm octopus look less "easily-nipped." Flounders
also stay close to the sandy sea floor, so an octopus acting like one is never
far from the safety of a quick burrow.

Where the octopuses come up with the behavior is also a
mystery, Hanlon said, though he does have one tantalizing clue. In 1978, he caught
a larval longarm and raised it to adulthood in the lab. The octopus sometimes
swam forward in a flounder-like position. It had never seen a flounder or
another octopus, suggesting that the behavior is innate, not learned.

The researchers hope to learn more about the Atlantic
longarm's predators and self-defense mechanisms, Hanlon said. The intracoastal
waterway in West Palm Beach, Florida, is a prime habitat for the species, and
he plans to visit soon in search of more video footage.

"Animals that live out on sand planes and mud planes
all have wonderful biological adaptations," Hanlon said. "When you do
find animals out there, they're doing something extraordinary."

Stephanie Pappas

Stephanie Pappas is a contributing writer for Live Science. She covers the world of human and animal behavior, as well as paleontology and other science topics. Stephanie has a Bachelor of Arts in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. She has ducked under a glacier in Switzerland and poked hot lava with a stick in Hawaii. Stephanie hails from East Tennessee, the global center for salamander diversity. Follow Stephanie on Google+.